Nitrocellulose-nitric ester explosives composition containing hydroxyalkyl ether of a polysaccharide

ABSTRACT

A HIGH EXPLOSIVE COMPOSITION COMPRISING AT LEAST ONE LIQUID EXPLOSIVE NITRIC ESTER GELATINIZED BY MEANS OF NITROCELLULOSE AND AT LEAST 1% BY WEIGHT OF AT LEAST ONE LOWER ALIPHATIC GLYCOL SELECTED FROM THE GROUP CONSISTING OF ETHYLENE GLYCOL DIETHYLENE GLYCOL PROPYLENE GLYCOL AND DIPROPYLENE GLYCOL SAID GLYCOL HAVING DISSOLVED THEREIN AN OXYGEN-SUPPLYING SALT AND BEING THICKENED BY A MATERIAL SELECTED FROM THE HYDROXYETHYL AND HYDROXYPROPYL ETHERS OF POLYSACCHARIDES AND MIXTURES THEREOF.

3,723,208 NITROCELLULOSE-NITRIC ESTER EXPLDSEVES COMPOSITIUN CONTAINING HYDROXYALKYL ETHER OF A POLYSACCHARIDE Errol Linton Falconer, Mont Saint-Hilaire, Quebec, Canada, assignor to Canadian Industries Limited, Montreal, Quebec, Canada No Drawing. Filed Feb. 29, 1972, Ser. No. 230,522 Int. Cl. C06b /00 U.S. Cl. 149-94 2 Claims ABSTRACT OF THE DISCLOSURE A high explosive composition comprising at least one liquid explosive nitric ester gelatinized by means of nitrocellulose and at least 1% by weight of at least one lower aliphatic glycol selected from the group consisting of ethylene glycol diethylene glycol propylene glycol and dipropylene glycol said glycol having dissolved therein an oxygen-supplying salt and being thickened by a material selected from the hydroxyethyl and hydroxypropyl ethers of polysaccharides and mixtures thereof.

The present invention relates to gelatin type dynamite compositions and more particularly to such compositions containing a reduced quantity of explosive liquid nitric ester.

Gelatin type dynamite compositions are produced by gelatinizing a liquid explosive nitric ester with nitrocellulose and adding thereto a number of solid materials principally carbonaceous materials oxygen-supplying salts and stabilizing agents. Generally the liquid explosive nitric ester employed is a mixture of nitroglycerin and other nitric esters such as ethylene glycol dinitrate the presence of which etfects properties such as the freezing point. Throughout the disclosure the term NG will refer to both pure nitroglycerin and to mixture of nitroglycerin with other liquid explosive nitric esters. The gelatin dynamites are mixed in a variety of mixers known to the art and because of the gelatinous nature of the mixed product these explosives are normally cartridged by an extrusion process into paper or other film-like packages. The resultant packaged product is a highly water-resistant explosive of great strength.

It is customary to include in gelatin dynamites oxygensupplying salts and oxidizable material in lieu of some NG. The oxygen salts commonly employed are ammonium nitrate and sodium nitrate. The addition of these nitrates provides both explosive power as well as the necessary oxygen for the combustion of the cartridging material and other combustible carbonaceous matter in the explosive mixture. It is generally desired particularly for underground applications that the total explosive package be oxygen balanced; that is that the quantity of oxygen available from the salts be equal to the total oxygen required to fully oxidize the oxidizable ingredients in the explosive mixture as well as the packaging wrapper. Ideally such oxygen-balanced compositions will yield on detonation only insignificant quantities of toxic gases such as carbon monoxide hydrogen sulfide and nitric oxides which are hazardous particularly in enclosed spaces such as underground mines.

The total quantity of oxidizing salts and other solid ingredients which may be used in gelatin dynamites is limited by a resultant reduction in plasticity cohesiveness and sensitivity of the explosive mixture. As the quantity of these added ingredients is increased the gel-phase NG/ nitrocellulose proportion decreases to a point where the resultant mixture may not be water-resistant cohesive and plastic. To overcome the problem of the loss of these properties in gelatin dynamites a variety of plasticizing and lubricating agents have been proposed in the prior nited States Patent fice art. These lubricants and plasticisers are generally high cost materials which can be used only in very small quantities since their liberal use tends to adversely efiect the properties of explosive compositions.

It has now been found that in gelatin dynamite explosive compositions the quantity of NG/nitrocellulose gelphase may be reduced with an accompanying increase in the proportion of other ingredients without adversely effecting the physical or explosive properties of the compositions by incorporating in the compositions a thickened lower aliphatic glycol which preferably has dissolved therein other ingredients and a major proportion of oxygen-supplying salts. The use of such a thickened glycol/ salt liquor in replacement for part of the normal quantity of NG gel-phase used in gelatin dynamite formulations has the desirable elfect of reducing the impact sensitivity of the explosive mixtures while maintaining plasticity, initiation sensitivity and other beneficial physical and explosives properties.

It is therefore an object of the invention to provide an improved highly waterproof gelatin dynamite explosive composition which contains a lower proportion of liquid nitric ester gel-phase than has heretofore been possible.

It is a further object of the invention to provide a freely extrudable gelatin dynamite composition which possesses conventional explosive properties and yet has a reduced sensitivity to impact and friction.

The improved gelatin dynamite compositions of this invention thus comprise at least one liquid explosive nitric ester gelatinized by means of nitrocellulose and at least 1% by weight of at least one lower aliphatic glycol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol, said glycol having dissolved therein an oxygen-supplying salt and being thickened by a material selected from the hydroxyethyl and hydroxypropyl ethers of polysaccharides and mixtures thereof.

Since the lower glycols employed as the gel-phase ex tenders in the present invention possess useful solubility properties towards the oxygen-supplying salts normally used in gelatin dynamites, the said salts may advantageously be predissolved in the thickened lower glycol. Examples of such salts are calcium, ammonium and sodium nitrates and sodium, calcium and ammonium perchlorates. Soluble fuels such as urea and formamide and mixtures of these may also be predissolved in the glycol. The presence of the oxygen-supplying salts provides some of the oxygen which is subsequently demanded for complete combustion during detonation of the explosive and hence makes easier the design of suitable oxygen balanced explosive mixtures.

While a number of polymeric and other colloidal thickeners for fluids are known and may be partly effective in thickening or gelling lower glycols, these are generally unsuitable for use in conjunction with the oxygensupplying salts found in explosive mixtures. For example, the inorganic colloidal thickeners such as pyrogenic silica results in unsatisfactory explosive products in terms of exudation. Soluble polymers such as polyoxyethylene resins are salt sensitive and are precipitated in the presence of dissolved oxygen salts. Only the series of the hydroxyethyl and hydroxypropyl ethers of polysaccharides have been found capable of providing non-exuding stable glycol gels in the presence of oxygen-supplying salts such as ammonium, sodium and calcium nitrate and perchlorates. The quantity of thickener employed with a given quantity of lower glycol is arbitrary and depends on the degree of thickness or plasticity desired. Generally from 0.2% to 10% by weight of thickener in the glycol can be used although the higher level will most often be beyond the degree of gelation normally useful in commercial gelatin dynamic explosives. Examples of polysaccharides,

the hydroxyethyl and hydroxypropyl ethers of which are suitable for use in the invention are glucose polysaccharides, mannose polysaccharides and galactose polysaccharides.

The following examples and tables illustrate the thickened glycol gel-phase of the invention and will show the desirable properties of gelatin dynamite explosive compositions containing the same.

EXAMPLE 1 Two gelling tests A and B were undertaken to evaluate the ability of several hydroxyalkyl ethers of polysaccharides to thicken ethylene glycol.

In test A, 10 grams of ethylene glycol and 1 gram of a polysaccharide derivative were mixed with stirring at room temperature in the presence of 5 grams each of sodium nitrate and ammonium nitrate, which nitrates are typical of those found in commercial explosive compositions.

A plastic-like self-supporting gel was formed as follows:

with hydroxyethyl guar, after 5 minutes; with hydroxypropyl guar, after 15 minutes; with hydroxyethyl cellulose, after 30 minutes.

In test B," a salt containing glycol-based liquor was prepared by dissolving 60 parts of technical grade calcium nitrate and 30 parts of ammonium nitrate in 55 parts of ethylene glycol, 23 parts of diethylene glycol and 25 parts of formamide, a useful liquid fuel ingredient. All salts were fully dissolved at room temperature. About one gram of a polysaccharide derivative was added to grams of the glycol-based liquor. Plastic-like self-supporting gels were formed as follows:

with hydroxyethyl cellulose, after 3 minutes; with hydroxyethyl guar, after 6 minutes; with hydroxypropyl guar, after 30 minutes.

Observation of the results of tests A and B emphasizes the unpredictability of the influence of soluble salts on the rates at which the gelling of the ethylene glycol liquor phase takes place. It can be observed, for example, that hydroxyethyl cellulose in test A produced a gelled glycol in 30 minutes in the presence of ammonium and sodium nitrate, While in test B the same derivative produced a gel in about 3 minutes in the presence of calcium and ammonium nitrate and formamide. The degree of gelatin and time in which it occurs is also effected by the degree of substitution (D.S.) as outlined by W. A. Jordan in US. Pat. No. 3,483,121 issued on Dec. 9, 1969. It was generally observed that the guar derivatives produced a cleaner gel than did the cellulose derivatives but all the gel types of the tests were useable in a wide range of gelatin explosive formulations.

In similar tests, propylene glycol and diethylene glycol were gelled by the addition of hydroxyethyl guar. Hydroxypropyl guar, hydroxypropyl cellulose and hydroxyethyl starch were found capable of gelling glycol solutions of oxidizer nitrate salts. Surprisingly it was noted that hydroxypropyl guar did not gel pure glycol. Only when salts were dissolved in the glycol did the hydroxypropyl guar produce effective thickening. Most of these thickening agents are generally available from commercial suppliers but, if desired, may be prepared in the laboratory or factory. Hydroxyethyl starch, for example, may be made by reacting equimolar proportions of corn starch, 2-chloroethanol and 40% sodium hydroxide in the presence of isopropanol. This preparation is typical of the preparation of hydroxyethyl derivatives of polysaccharide compounds described in the chemical literature.

As noted heretofore, the most useful of the gel-phase matrices in gelatin explosive compositions are those havmg relatively the least oxygen values. The lower aliphatic glycol liquid component of the gel-phase matrix of the p e n en on has a ge e t sea demand for mplete combustion. For example, ethylene glycol, diethylene glycol and propylene glycol have oxygen values respectively of l29, l5l, and 168. Less negative values than those exemplified would be advantageous in the design of explosives. In order to provide a liquid component of more suitable oxygen balance for the gel matrix, a lower aliphatic glycol liquor containing oxidizing salts may be prepared. A series of such liquors is shown in Table I below. These mixtures may be described as glycol-based solutions of oxidizer salts or lower amine nitrates. While nitrate salts are shown in the table, perchlorate salts such as sodium, calcium and ammonium perchlorate may also be employed since these perchlorates have useful solubilities in the lower glycols. The proportions shown in Table I are in percent by weight.

TABLE I Liquor A B C D E F G H Ethyleneglycol 39 36 35.5 35 34 33.5 24.5 24.5 Calcium nitrate (technical) 43 38 37.5 37 36 35.5 30.0 30.0 Ammonium nitrate... 18 26 27.0 20 26 25.0 31.5 30.0 Sodium nitrate 2 4 6.0 5.0 5.0 Formamide 4.0 10.5

Crystallization point TABLE II Liquor A B C D E Ethylene glycol 28.0 28. 0 33.0 13.5 11.6 Diethylene glycol 12. 0 12.0 5.0 4. 3 3. 6 Fonnamide 13.0 15. 0 8.0 7. 1 Urea 13.0 Calcium nitrate (technical). 30.0 30.0 30.0 16.0 19. 0 Monomethylaminc nitrate 48. 0 42. 5 Ammonium nitrate 15. 0 15.0 15.0 8.0 14. 2 Surfactant 1.0 1.0 1.0 1.1 1.0 Hydroxypropyl guar 1.0 1.0 1.0 1.1 1.0

Oxygen value 53 52 51 42 29 Crystallization point F 58 68 52 77 63 All of the liquors shown in Table II possess lower oxygen balances compared with ethylene glycol or other glycols. The lower crystallization points, compared to the liquors of Table I, indicate an increased dissolution therein of useful oxygen-supplying salts at reduced temperature's.

As noted hereinbefore, the thickened glycol gel-phase of the present invention, preferably containing dissolved oxygen-supplying material, may be used as a nitroglycerin extender in typical gelatin dynamite compositions. This utility is demonstrated in Example 2 and Table III below.

EXAMPLE 2 Varying amounts of liquor A as shown in Table II were employed in the preparation of gelatin dynamite compositions. These compositions were typical of commercial gelatin dynamite explosives in terms of consistency, density and power, yet they contained substantially less nitroglycerin then normal commercial compositions having the same properties. The compositions shown in Table III below demonstrate the elfect of the use of various amounts of nitroglycerin sensitizer and glycol liquor in the mixtures. In all of the formulations shown, the percentage of nitroglycerin plus nitrocotton plus glycol liquor equals about 30 percent by weight of the final compositron. The nitroglycerin used Was the common commercial low-freezing mixture of ethylene glycol diuitrate and glycerol trinitrate. The proportions shown in Table III are in percent by weight.

TABLE III Formulation 1 2 3 4 N itroglycerin 9. 9. 6 ll. 0 14. 0 Nitrocotton 0. 4 0. 4 O. 4 0. 4 Glycol liquor A 20. 0 19. 8 15. 4 15.3 Ammonium nitrate 51. 4 51. 0 51.0 6 4 @{odum nitrate 18. 4 18. 4 13% g y roxypro yl uar- 0. 0.5

Chalk 305 0. 3 0. 3 0.3 0.3

Density (gJr-c.) 1. 36 1. 40 1 42 Impact test (inches) 7. 54 7. 54 7. 54 7. 54

Min. initiator in 1% dia. cartridge:

At 70 F SEB GEB GFC P 10P BEB IFC 8EB=Commercial No. 8 electric blasting cap. FC=Standard fulminate-ehlorate test cap. 10P=1O grams of pentolite (60/40 PETN [TN T).

The formulations recorded in Table III will be recognized by those skilled in the art as having substantially less nitroglycerin sensitizer than the common commercial gelatin dynamites of corresponding density and initiation sensitivity. During testing, it was estimated that wihout the use of the glycol based gel-phase, or more of liquid nitroglycerin would be required to prepare compositions of the same degree of plasticity and extrudability. It was also observed that these reduced nitroglycerin compositions retained good initiator sensitivities yet all exhibited a substantial reduction in sensitivty to mechanical impact. None of the glycol liquor-containing compositions shown in Table III could be detonated by the impact of a five kilogram weight falling a height of 54 inches onto a A inch diameter pin or by the glancing blow of a ten pound steel torpedo sliding 60 inches down a 45 frictionless incline. In contrast, commercial gelatin dynamite compositions commonly detonate in both these tests from heights of 20-30 inches or even lower depending on the formulation. It was also observed during the preparation of the compositions shown in Table IH, that the characteristic odor of nitroglycerin was less obvious in the finished cartridge and that a reduced toxic response was experienced by a number of exposed individuals compared to regular gelatin dynamite formulations. This was attributed to a reduction in the quantity of nitroglycerin present, together with an ability of the glycol based gel-phase to act as a type of barrier to the evolution of toxic fumes.

EXAMPLE 3 A series of nitroglycerin-sensitized formulations identical to those shown in Table III were prepared except that the hydroxypropyl guar thickener was replaced by hydroxyethyl guar (available from Stein-Hall Corp., New York). Substantially similar performance results were obtained. It was observed that slightly less time was required to produce compositions of the desired plasticity when hydroxyethyl guar was employed.

As is well known in the explosive industry, there is a demand for gelatin dynamite explosives of reduced initiation sensitivity for use with certain blasting techniques and as so-called safety explosives. To produce such products the industry has generally added to a gelatin dynamite formulation a small quantity of a nitroaromatic compound such as dinitrotoluene (DNT). In contrast to the nitroglycerin compositions described in Examples 2 and 3, a series of compositions of reduced initiation sensitivity were prepared and are described below in Example 4 and Table IV.

6 EXAMPLE 4 Varying amounts of liquor C as shown in Table H were employed in the preparation of gelatin dynamite compositions of reduced initiation sensitivity. Care was taken during the mixing of the formulations to fully pregelatinize the nitroglycerin with the nitrocotton so that no free explosive liquid could be absorbed ino the porous ingredients. Ingredients with fatty or hydrophobic surfaces were also avoided in order to avoid uncontrolled sensitization. The compositions shown in Table IV demonstrate the controlled sensitivities possible with the simultaneous use of DNT and a glycol based gel-phase as desensitizing components. The proportions shown are in percent by weight.

TABLE IV Formulation Glycol liquor Ammonium nitratefin HNOOHO z pe w g, OOOOOIO q OUIOCHOIOIOO N Density (g./ce.) Oxygen balance (unwrapped) Min. initiator in 1% paper cartridges 1 High strength detonator.

An examination of the formulations given in Table IV shows that the sensitivity to initiation of a gelatin dynamite may be controlled by the use of DNT and the glycolbased gel-phase of the invention. Such compositions possess all the physical and strength characteristics of conventional gelatins, and will enjoy increased commercial acceptance because of their reduced degree of hazard.

As has been disclosed and exemplified the thickened glycol liquor of the present invention may be suitably employed as a part replacement and extender for the nitroglycerin sensitizer in gelatin dynamite compositions resulting in an improved and safer product having lowered toxicity and a reduced sensitivity to mechanical impact.

What I claim is:

1. A high explosive composition comprising at least one liquid explosive nitric ester gelatinized by means of nitrocellulose and at least 1% by weight of at least one lower aliphatic glycol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol, said glycol having dissolved therein an oxygen-supplying salt and being thickened by a material selected from the hydroxyethyl and hydroxypropyl ethers of polysaccharides and mixtures thereof.

2. An explosive composition as claimed in claim 1 wherein the polysaccharide is selected from the group consisting of glucose polysaccharides, mannose polysaccharides, galactose polysaccharides and mixtures thereof.

STEPHEN J. LECHBRT, IR., Primary Examiner US. Cl. X.R.

UNITED STATES PATENT ()FFICE 2 CERTIFICATE OF CORRECTION Patent No. 5,723,208 Dated March 27, 1973 Inventofls) Errol Linton Falconer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, lines, after "Sen No. 250 522 add the following: I Claims priority application Canada, March 15, 1971, Ser. No. 107,776

Signed and sealed this 5th dayof November 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents F ORM PO-1050 (10-69) USCOMM-DC 60376-P69 u.5, GOVERNMENT PRINTING OFFICE: was o-sss-aa4.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,725,208 Dated March 27, 197;

Inventor(s) Errol Linton Falconer It is certified that error appears in the above-identified patent and'that said Letters Patent are hereby corrected as shown below:

Column 1, 1ine8, after "sen No. 250,522 add the following: Claims priority application Canada, March 15, 1971, Ser. No. 107,776

Signed and sealed this 5th day of November 1974.

v (SEAL) Attest:

McCOY M. GIBSON JR.

C. MARSHALL DANN Attesting Officer Commissioner of Patents 3 FORM PC4050 (10-69) USCOMM-DC GOING-P69 us. GOVERNMENT PRINTING OFFICE: 1959 o-ass-sn. 

